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Evaluation of a fetus for structural or functional heart disease
is commonplace, as the application of clinical fetal ultrasound
has become widespread in modern obstetrical practice. Furthermore, our
current understanding of the genetic basis for congenital heart
defects prompts screening in patients who otherwise might not have
been referred for evaluation in the past. It is important to understand
the uses and limitations of fetal echocardiography to optimally
utilize this technology and to provide appropriate counseling to
parents. The purpose of this chapter is to provide a brief overview
of fetal cardiology that can be used as a foundation for understanding
selected aspects of fetal heart disease. More comprehensive references
on fetal cardiology and, in particular fetal echocardiography, are
listed at the end of this chapter.

Fetal echocardiography is the primary method for diagnosing fetal
cardiovascular disease and monitoring progression and management
of the disease process. This chapter will provide a succinct overview
of fetal echocardiography to provide basic information about its
indications and limitations, and will discuss how to apply findings
from a fetal echocardiogram to the patient. Additional information
about the application of echocardiography to assess cardiac and
vascular function in the fetus is presented in Chapter 3.

A complete fetal echocardiogram is similar in scope to a postnatal
transthoracic echocardiogram. Cardiac and great vessel anatomy and
relationships, cardiac function, blood flow patterns, and cardiac
rhythm are all assessed. A wide range of cardiovascular diseases
can be detected and defined in the fetus, including simple and complex
cardiovascular structural malformations, cardiomyopathies, tumors,
and arrhythmias. Newer techniques of three- and four-dimensional echocardiography
are being applied in many centers, but at present, the role of these
modalities in improving detection, management, and follow-up requires
additional research.

If indicated (see subsequent discussion), the first fetal echocardiogram
is generally performed around 18- to 20 weeks gestation using a
standard transabdominal approach. In some centers, transvaginal
fetal echocardiography is offered as early as 11 weeks gestation.
However, controversy exists regarding the usefulness of early transvaginal
ultrasound and it is not widely used at present. Transabdominal
studies performed at around 18 to 20 weeks gestation provide excellent resolution
of the cardiovascular structures and are sufficiently early in gestation
so that elective termination can be considered if the family so
desires.

Indications

As discussed in Chapter 15, the incidence of congenital cardiovascular
malformations in the United States is around 10 per 1000 live births.
The incidence of structural cardiovascular malformations in all
pregnancies is not known precisely, but it is most certainly higher
for at least three reasons: (1) severe structural or functional
cardiovascular malformations may not permit survival of the fetus;
(2) some mothers elect to terminate the pregnancy if an extracardiac
malformation or chromosomal abnormality is detected; and (3) the
structural defect may be subtle or even nonexistent in the fetus,
and may manifest only after birth when the circulation transitions
to ...